Conventionally, there has been known an antenna device that is formed on a board as a surface pattern, such as a microstrip antenna. The antenna device includes, for example: radiating elements that radiate radio waves; and a main line that supplies electric power, which is supplied from a controller of a radar apparatus etc., to the radiating elements (see, e.g., Japanese Laid-open Patent Publication No. 2016-086432).
In such an antenna device, for example, shapes and/or element widths of the radiating elements are changed for each of the radiating elements so as to adjust a distribution ratio of electric-power to be supplied to the radiating elements, and thus the directivity of radio waves is designed to be low side lobe.
However, when matching elements are used for the radiating elements in order to realize a desired electric-power distribution ratio, for example, an impedance adjusting circuit is to be additionally provided to each of the elements, and thus the configuration becomes complicated. Moreover, when the element widths of the radiating elements are changed, there exists possibility that the robustness is reduced due to effects of manufacturing tolerance. As described above, conventionally, there exists possibility that an antenna shape becomes complicated in order to achieve the desired electric-power distribution ratio.